Generally, a chemical mechanical polishing (CMP) tool is a tool to be mainly used in semiconductor manufacturing processes and is known to be a polishing tool for a highly fine flattening process to remove the steps between multiple wiring layers of a wafer surface through a mechanical polishing and a chemical reaction.
To describe a general structure of a CMP tool briefly, a CMP tool comprises a platen (a polishing table) on which a polishing pad (resilient polishing paper) is attached to; a polishing carrier (a polishing head) for pressing downward and being rotated while gripping a wafer to make a mutual contact between the polishing pad and a surface of the wafer; a slurry supply nozzle for providing slurry onto the polishing pad; and a conditioner carrier for gripping and rotating a dressing conditioner which prohibits a shape change or contamination of a surface of the polishing pad so that polishing performance of the polishing pad is continuously maintained. The CMP tool is designed to physically flatten convex and concave portions of a wafer surface by moving the platen and the polishing carrier relatively while supplying slurry onto the wafer surface and reacting slurry with the wafer surface chemically under a condition that a wafer is contacted with a surface of the polishing pad.
Currently, a study on the CMP tool is actively going on to improve performance of each member thereof. In this end, the applicant of the present application suggested “a multiple fluid supplying apparatus for polishing and conditioner carriers of a polishing system of semiconductor wafer” described in Korean patent application No. 2003-39627 (hereinafter referred to '627 application), where a rotary union is applied to flow slurry while maintaining a high airtight sealing between a non-rotating body and a rotating body during a relative movement between respective members thereof.
The structure of a multiple fluid supplying apparatus suggested in '627 application comprises a rotary union at a driving side wherein a hollow rotation axle being formed with a plurality of through-holes is installed and rotated on a non-rotatable, central fixed axle formed with a fluid path, a non-rotatable sealing housing for support is installed which supports the hollow rotation axle on an outer circumference thereof and exhausts operational fluid outside, and a dual structured stack-type sealing rod is provided which is closely intervened in a stacked manner respectively at an inner and an outer sides of the hollow rotation axle for maintaining air-tightness between the central fixed axle, the hollow rotation axle and the sealing housing, a spindle which is combined with the hollow rotation axle and is capable of rotating about the outer circumference of the hollow rotation axle without interference therewith; a spindle housing for supporting the spindle; a driving device for rotating the hollow rotation axle and the spindle, respectively; a rotary union at a following side wherein a sealing housing being formed with a plurality of through-holes is installed on a central rotation axle being formed with a plurality of fluid paths combined integrally with carrier axles of a plurality of carrier connection members which are provided symmetrically about the central fixed axle in the spindle in order to supply operational fluid to the carrier connection members so that the rotary union at the following side is supported in a non-rotational condition by a bracket connected to the sealing housing of the rotary union at the driving side, and a stack-type sealing rod with a single-layered structure is provided which is closely intervened in a stacked manner between the central rotation axle and the sealing housing for maintaining air-tightness therebetween; a plurality of conduits for connecting the through-holes together formed in the respective sealing housings of the rotary union at the driving side and the rotary union at the following side; and a power transfer member for transferring rotational force from the rotary union at the driving side to the respective carrier connection members.
However, the rotary union structure suggested in the '627 application has some problems. That is, in the rotary union structure at the driving side, one end of the central fixed axle formed with a fluid path is supported on top of the spindle housing by way of a bracket, while the other end thereof is supported by an inner circumference surface of the hollow rotation axle, and power is transferred by engaging a driving belt with the hollow rotation axle of the outer circumference thereof so that the support condition of the central fixed axle for flowing fluid is unstable. This causes a rolling (or run-out) between both ends of the central fixed axle or the hollow rotation axle when rotational force is transferred to the hollow rotation axle so that a phenomenon that a sealing portion between a rotating body and a non-rotating body is partially separated from or excessively contacted with each other in an irregular manner repeatedly occurs which leads to a risk of operational fluid leakage due to uneven abrasion of a sealing member itself. This may be caused by a severe rolling phenomenon due to a weak structure in which the respective sealing housings of the rotary union at the driving side and the rotary union at the following side are connected simply by a bracket.
Yet another problem in the rotary union structure at the driving side is that the inner and outer circumferential surfaces of the hollow rotation axle which correspond to a contact portion of a rotational body and a non-rotational body to be sealed are dually sealed so that the structure thereof becomes complicated and there is a high possibility of operational fluid leakage due to a widened area for maintaining air-tightness compared with a single-layered sealing structure as well.
Yet another problem in a sealing structure of a contact portion between a rotational body and a non-rotational body of the rotary union structure at the driving side or at the following side is that, in the multiple fluid supplying apparatus suggested in '627 application, like a prior art, the sealing member is transformed by heating due to physical friction of the sealing member and is continuously abraded as well and therefore air-tightness thereof is gradually worsened.
Yet another problem is that the carrier axles of the respective carrier connection members are received in an inner space of the spindle and thus it is inconvenient and cumbersome because the whole apparatus must be disassembled when maintenance thereof is required.